The invention relates to a flotation device for separating materials or mixtures of materials from suspensions in order to form at least one high material content fraction and one low material content fraction, with several rotationally symmetrical plates arranged one above another in a flotation tank, wherein during the separation procedure the low material content fraction enters into the plate spaces between the plates and arrives at a clarified fluid collection tube, and horizontally outside the plates a vertically extending annular separating space is formed that communicates with a run-off provided above the plates for the high material content fraction.
A flotation device of rectangular plan is known from U.S. Pat. No. 3,182,799, in which there are outwardly orientated plates, wherein in the space between each two plates there is a suspension inlet above, and beneath this a clarified fluid outlet, wherein between the inlet and outlet there are short deflecting plates. This arrangement has the disadvantage that because of the dimensioning of the deflecting plates in particular, with elevated hydraulic loading (high pressures or throughputs) a xe2x80x9cshort-circuit flowxe2x80x9d occurs from the inlet to the outlet that drastically impairs the separation efficiency. Further, cleaning of the installation, as is necessary in particular in the paper industry when colours are changed, is very complex due to the separate supply lines.
Proceeding from this, the object of the invention is to provide a flotation device as described in the preamble, which avoids the disadvantages described hereinabove, and is distinguished in particular by efficacious separation of the desired materials from the suspension into a high material content fraction and a low material content fraction.
This object is solved according to the features described in claim 1. Advantageous further developments will be evident from the dependent claims.
The substantive advantages of the invention are in that the surface area of the installation is reduced in comparison with horizontal flotation devices, and thus the flotation capacity is greater per surface area of the installation. By combination of the plate arrangement and the eccentrically loaded reaction and mixing space, there is improved flocculation, and thus better processing values, in the filtrate. By separating using the double plate principle, better separation values are obtained.